Letter from Greece, from air hostess (3)
I believe the answer is:
rho
'letter from greece' is the definition.
(letter from the Greek alphabet)
'from air hostess' is the wordplay.
'from' indicates the answer is hidden within the clue.
'RHO' is hidden within 'air hostess'.
(Other definitions for rho that I've seen before include "Sophocles character" , "Greek P" , "Greek letter used as symbol for density" , "Something like 25 [ETA]" , "Greek letter R" .)